Rationale and design of the RIACT-study: a multi-center placebo controlled double blind study to test the efficacy of RItuximab in Acute Cellular tubulointerstitial rejection with B-cell infiltrates in renal Transplant patients: study protocol for a randomized controlled trial.

BACKGROUND: Acute kidney allograft rejection is a major cause for declining graft function and has a negative impact on the long-term graft survival. The majority (90%) of acute rejections are T-cell mediated and, therefore, the anti-rejection therapy targets T-cell-mediated mechanisms of the rejection process. However, there is increasing evidence that intragraft B-cells are also important in the T-cell-mediated rejections. First, a significant proportion of patients with acute T-cell-mediated rejection have B-cells present in the infiltrates. Second, the outcome of these patients is inferior, which has been related to an inferior response to the conventional anti-rejection therapy. Third, treatment of these patients with an anti-CD20 antibody (rituximab) improves the allograft outcome as reported in single case observations and in one small study. Despite the promise of these observations, solid evidence is required before incorporating this treatment option into a general treatment recommendation. METHODS/DESIGN: The RIACT study is designed as a randomized, double-blind, placebo-controlled, parallel group multicenter Phase III study. The study examines whether rituximab, in addition to the standard treatment with steroid-boli, leads to an improved one-year kidney allograft function, compared to the standard treatment alone in patients with acute T-cell mediated tubulointerstitial rejection and significant B-cell infiltrates in their biopsies. A total of 180 patients will be recruited. DISCUSSION: It is important to clarify the relevance of anti-B cell targeting in T-cell mediated rejection and answer the question whether this novel concept should be incorporated in the conventional anti-rejection therapy. TRIAL REGISTRATION: Clinical trials gov. number: NCT01117662.

The effect of cinacalcet on bone remodeling and renal function in transplant patients with persistent hyperparathyroidism.

BACKGROUND: Parathyroidectomy is associated with renal functional losses in transplant patients; cinacalcet offers an attractive alternative. METHODS: We performed a prospective observational study in 58 patients with persisting hyperparathyroidism after renal transplantation (Ca≥2.6 mmol/L) and impaired renal transplant function (estimated glomerular filtration rate [eGFR] <50 mL/min). The patients received 30 to 90 mg cinacalcet for 12 months with the target to normalize serum Ca. We measured parathyroid hormone (PTH), serum Ca, serum phosphorus, alkaline phosphatase, bone-specific alkaline phosphatase, osteocalcin, and telopeptide at 0, 1, 2, 3, 6, 9, and 12 months of cinacalcet treatment. Fractional excretion of calcium and phosphorus (n=24) were monitored at 0 and 1 month. RESULTS: At inclusion, creatinine was 181±70 µmol/L, eGFR 43±19 mL/min, PTH 371±279 pg/mL, and Ca 2.73±0.22 mmol/L. We observed nephrocalcinosis in 58% of biopsied patients at enrollment. After cinacalcet, Ca decreased significantly and normalized at nearly any measurement. Phosphorus increased significantly at months 1, 9, and 12. PTH decreased significantly, but only at months 9 and 12 and did not normalize. Bone-specific alkaline phosphatase increased significantly (>normal) by month 12. eGFR decreased and serum creatinine increased at all time points. The Δ(creatinine) % increase correlated significantly with the Δ(PTH) % decrease at month 1 and 12. Telopeptide and alkaline phosphatase correlated with PTH and telopeptide also correlated with serum creatinine. CONCLUSION: Calcium-phosphorus homeostasis in hypercalcemic renal transplant patients normalizes under cinacalcet and PTH decreases, albeit not to normal. The renal functional decline could be PTH mediated, analogous to the effects observed after parathyroidectomy.

Renal cell carcinoma in transplant recipients with acquired cystic kidney disease.

BACKGROUND: Acquired cystic kidney disease (ACKD) is a widely known renal cell carcinoma risk factor. DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS: An ultrasound screening of the native kidneys in all renal transplant patients of a renal outpatient clinic who received a transplant between 1970 and 1998 and presented between 1997 and 2003 (n = 916) was initiated prospectively. A total of 561 patients were screened. RESULTS: A total of 129 (23%) patients had ACKD; 46 (8.2%) patients had complex renal cysts (Bosniak classification, category IIF to III); and eight (1.5%) patients had newly diagnosed renal cell carcinoma, seven of which were associated with ACKD (category IV). One patient had renal cell carcinoma in the transplanted kidney. Together with 19 patients of the cohort with formerly diagnosed renal cell carcinoma (18 of them associated with ACKD), the prevalence of renal cell carcinoma among all patients was 4.8%; among the patients with ACKD, it was 19.4% (without ACKD 0.5%; P = 0.0001); and among the patients with complex renal cysts (category IIF to III), it was 54.4%. The patients with ACKD were older (54 +/- 13 versus 51 +/- 14 yr; P = 0.048), more often male (65 versus 54%; P = 0.03), more often had heart disease (44 versus 29%; P = 0.001), had larger kidneys (6.9 and 6.8 cm versus 6.0 and 5.9 cm; P < 0.001), and had more calcifications (29 versus 15%; P = 0.002). Renal cell carcinoma was bilateral in 26% of cases. Tumor histology was clear cell carcinoma in 58% and papillary carcinoma in 42% of cases; one patient had both. Only one patient had a lung metastasis, and no patient died. CONCLUSIONS: Renal cell carcinoma occurs often after renal transplantation and that especially patients with ACKD should routinely be screened. Because ACKD after renal transplantation seems to be less frequent (23%) than during dialysis treatment (30 to 90%), renal transplantation may inhibit renal cell carcinoma.

Decreased renal transplant function after parathyroidectomy.

BACKGROUND: Persistent secondary hyperparathyroidism after renal transplantation may require parathyroidectomy (PTX). Clinical experience suggests that these patients commonly develop decreased renal function thereafter. METHODS: To test this notion, we evaluated 76 transplant patients who underwent pararhyroidectomy between 1997 and 2003. RESULTS: In half the patients (47%), creatinine clearance decreased >20% (before vs after PTX, 57 +/- 21 vs 38 +/- 17 ml/min, P = 0.001). The patients with decreased creatinine clearance had higher parathyroid hormone (PTH) concentrations before and lower values after PTX compared with those who did not (594 +/- 392 vs 447 +/- 234 pg/ml before PTX, P = 0.03; 35 vs 123 pg/ml thereafter, P = 0.002). They also had lower serum calcium concentrations after PTX (2.0 vs 2.2 mmol/l, P = 0.005) and they required more calcium and vitamin D analogues. These patients also more commonly underwent total PTX with autotransplantation, compared with subtotal (75 vs 50%, P = 0.03). However, in multivariate analysis, only the delta PTH decline (%) after PTX was a significant predictor of deteriorating renal function (P = 0.005) and was correlated with the creatinine clearance decrease (R = 0.369, P = 0.001). Prospectively measured inulin and para-amino-hippuric acid (PAH) clearance decreased significantly after PTX in a subgroup of 19 patients (inulin before vs after PTX 67 vs 55 ml/min/1.73 m(2), P = 0.001; PAH 360 vs 289 ml/min/1.73 m(2), P = 0.001). Transplant biopsies revealed calcification in 70% of biopsied cases. CONCLUSION: Since PTH has a known positive regulatory effect on renal perfusion and glomerular filtration rate, we conclude that relative hypoparathyroidism after PTX is the main mechanism contributing to decreased renal function in these patients. There was no difference in 10-year-graft survival between the deteriorating and the non-deteriorating group.

Growth arrest specific protein 6/Axl signaling in human inflammatory renal diseases.

BACKGROUND: Growth arrest-specific gene 6 (Gas6) and its binding partner, the receptor tyrosine kinase Axl, are important mediators in experimental nephritis. The authors tested whether the Gas6/Axl signaling pathway participates in human renal diseases. METHODS: The authors compared 26 human renal specimens from patients with IgA nephritis, acute diffuse immune complex glomerulonephritis, acute lupus nephritis, antineutrophil cytoplasmic antibody--associated glomerulonephritis, acute transplant rejection, and normal renal tissue. Because reactive oxygen species are pivotal in inflammation, the authors tested whether the Axl/Gas6 expression is influenced by NADPH oxidase in vitro. RESULTS: Gas6 and Axl immunofluorescence was barely detectable in normal kidney. However, in disease Axl was copiously expressed in the small vessel media, glomeruli, distal tubules, and collecting ducts. Similarly, Gas6 was upregulated in the small vessel intima and media, all segments of the renal tubules, the brush border, and glomeruli. Gas6 and Axl upregulation was a prominent but nonspecific finding in these renal diseases. Cultured rat vascular smooth muscle cells and immortalized human mesangial cells were stimulated with angiotensin (Ang) II (1 x 10(-7) mol/L) for 6 or 18 hours. Confocal microscopy and Western blot showed Ang II-dependent Gas6 and Axl expression. An antisense probe against the p22 phox unit of NADPH-oxidase suppressed Ang II-induced Gas6 and Axl expression. In addition, in p47 phox knockout cells Ang II-induced Gas6 and Axl expression were blocked. CONCLUSION: GAS6/Axl signaling is involved in human renal disease. The Ang II-induced Gas6 and Axl expression may be dependent on NADPH-oxidase. Gas6 and Axl are important signaling molecules in human renal disease and may be potential therapeutic targets.

Expression of A20 in the vessel wall of rat-kidney allografts correlates with protection from transplant arteriosclerosis.

BACKGROUND: Chronic rejection with development of transplant arteriosclerosis is the major culprit involved in loss of kidney allografts. The allografts' fate was thought to depend on the intensity of the host immune responses and the potency of immunosuppressive regimens. Recent data suggests that grafts contribute to their own survival by way of up-regulation of "cytoprotective" genes. METHODS: We analyzed the expression of four cytoprotective genes, A20, Bcl-2, Bcl-x(L) and heme oxygenase (HO)-1, in three rat renal allograft models of chronic rejection: Fisher 344-Lewis (F344/Lew), Dark Agouti-Brown Norway (DA/BN), and DA-Wistar-Furth (WF). We chose these genes for their known anti-inflammatory and anti-apoptotic function in endothelial cells (EC) and the atheroprotective function of A20 in smooth muscle cells (SMC). RESULTS: Twenty-eight and 9 weeks following transplantation, F344/Lew and DA/BN transplants had stable graft function. Histopathologic analysis showed moderate tissue damage, minimal cellular infiltrates, and preserved vascular integrity correlating with high expression of A20 in SMC. Conversely, impaired allograft function in the DA/WF combination with substantial transplant arteriosclerosis was noted in 60% of the grafts correlating with absent or decreased A20 expression in EC and SMC. In all combinations, expression of HO-1, Bcl-2, and Bcl-x(L) colocalized with infiltrating cells and was not informative on the graft status. CONCLUSIONS: We demonstrate for the first time a strict correlation between A20 expression in the vessel and the absence of transplant arteriosclerosis in rat kidney-allograft models. This data is similar to data obtained in human kidney allografts and suggests that A20 may represent a novel therapeutic target for the prevention of chronic allograft rejection.